As a battery becomes older, it becomes less able to hold charge. It is therefore useful to be able to determine the state-of-charge of a battery.
A known method for estimating the state of charge of a cell of a battery can be found in L. Plett, et al.: “Extended Kalman filtering for battery management systems of LiPB-based HEV battery packs”, Journal of Power Sources, 2004, page 252-292. This article will be referred to herein as “Plett 2004.”
Known methods of such estimation involve matrices that represent state noise and measurement noise. In practice, it is difficult to set these matrices. This is particularly true for the state noise matrix since it is difficult to quantify the modelling error a priori.